What differentiates your theory here from the millions of incorrect theories we heard 8 years ago?
For the most part, Trumps first presidency was normal. The biggest thing people say against it is generally that the US wasn't prepared for the pandemic. Well, no one was, I'm not sure why anyone would think a Democrat in the White House would have changed everything.
The main overarching themes of criticism were that Trump had an autocratic mentality, looked up to dictators, appeased foreign interests, would paralyze federal agencies, and wouldn't be quick to step away from power. Those dynamics actually did end up playing out, with things like just standing by while China destroyed Hong Kong a few decades early, race riots were inflamed by a federal rejection of law and order, divisive anti-leadership during Covid, and culminating in what is hard to explain as anything other than a coup attempt when his poor performance cost him the election. Even being a libertarian (and highly sympathetic to many of the issues he was building support by paying lip service to), given that we all take the US/USG-led western order for granted for our generally high standard of living, and given that China (and its junior partner Russia) have been all too happy to step into any power vacuums made by our missteps, I'm highly inclined to not pull the threads of western civilization any further.
Ukraine is going to be fine. Taiwan is going to be fine.
Say by 2029 when Vance certifies himself as President.
Yeah, but's only true if you believe in the American-led world order and organizations like NATO. We know Trump either doesn't care or is actively hostile (he loves to threaten pull out of NATO and things like that).
There should be no doubt that he'll pull all support for Ukraine on Day 1. Ukraine will survive because they're already fighting and will still have the support of Europe, though that won't be enough to win. Taiwan will be actively pressured to capitulate without a shot. It will be "fine" the way Hong Kong is "fine".